The present invention relates to a method for the preparation of a protein in a biologically active or native form.
Recombinant DNA technology provides potentially extremely valuable means of synthesizing amounts of desirable eukaryotic (usually mammalian) proteins such as hormones, interferons, and enzymes. Although it has proved to be relatively easy to manipulate organisms such as bacteria to produce the desired protein, the host organism may not secrete the over-produced protein product into the culture medium. Thus physical or chemical lysis of the organisms (for example bacteria), followed by mechanical isolation of the insoluble desired protein is usually necessary. In the prior art, solubilization of the insoluble protein then proceeds with high concentrations of denaturants such as an aqueous urea or guanidine hydrochloride (International patent application WP 83/04418). Thus, solubilization has been conducted with relatively pure forms of the desired protein being obtained by a multistep process. Such processes are capital intensive and are best avoided when applied industrially.
In copending Australian patent application 66874/86, applicants have described a highly advantageous, albeit multistep, economical method for the recovery of proteins in a soluble form from an insoluble protein source utilising a cationic surfactant. While this process allows for the efficient recovery of proteins in a soluble form, the ultimate recovery of active protein has been limited. For example, the overall recovery is normally less than 50%. Significant losses may occur in the collection of host cells, their lysis and concentration of protein aggregates thus released via physical concentrative methods including differential centrifugation.